The invention relates to apparatus for receiving, storing and outputting digital signal sequences. Each digital signal may represent a test pattern and sequences thereof may, for example, be used for testing digital electronic devices of various kinds. One such apparatus has been disclosed in the German Patent No. 1220474. Therein the storing and outputting is effected by means of shift registers. For adjusting the digital signals, the output of each such shift register is provided with a switching arrangement. For adjusting the length of the sequence further switching arrangements are provided. This allows for freely modifiable digital signal sequences to be generated; however, a large number of switches are necessary which leads to appreciable space requirements, and also to a complicated set-up.